Fuel pump

ABSTRACT

An engaging hole-of an impeller, which receives a shaft, is formed by an impeller first planar surface, which is contactable with a shaft first planar surface, an impeller second planar surface, which is contactable with a shaft second planar surface, and an impeller first curves surface-and an impeller second curved surface, which connect between the shaft first planar surface-and the shaft second planar surface. A first groove and a second groove, which are communicated with the engaging hole, are formed in the impeller first curved surface and the impeller second curved surface, respectively. When the shaft first planar surface contacts the impeller first planar surface upon rotation of the shaft in one direction, the first groove is deformed by an applied force. Thereby, the shaft second planar surface and the impeller second planar surface contact with each other.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and incorporates herein by reference Japanese Patent Application No. 2013-196615 filed on Sep. 24, 2013 and Japanese Patent Application No. 2014-095859 filed on May 7, 2014.

TECHNICAL FIELD

The present disclosure relates to a fuel pump.

BACKGROUND ART

There is known a fuel pump that includes an impeller, which is rotatable in a pump chamber, and a motor, which generates a drive force to rotate the impeller. The fuel pump pumps fuel of a fuel tank to an internal combustion engine through rotation of the impeller. The patent literature 1 recites a fuel pump that includes an impeller. The impeller includes an engaging hole, which has a cross section of a D-shape and receives a shaft of an electric motor, and a hole, which receives a weight that corrects weight distribution of the impeller.

In a case of the fuel pump, which uses a brushless motor as the motor, the shaft is rotatable in two opposite directions, i.e., a normal direction, which is a rotational direction at the time of pressurizing the fuel with the impeller, and a reverse direction, which is a rotational direction at the time of sensing a rotational position of the rotor relative to the stator. A manufacturing tolerance exists in a size of the engaging hole of the impeller. Therefore, a gap is formed between an inner wall of the impeller, which forms the engaging hole, and a side wall of one end portion of the shaft, which is received in the engaging hole. When the operational state of the brushless motor is changed from one state, in which the one end portion of the shaft is rotatable in one of the normal direction and the reverse direction, to another state, in which the one end portion of the shaft is rotatable in the other one of the normal direction and the reverse direction, the shaft is rotated in the engaging hole, so that a rotational torque of the shaft, which is rotated with an accelerating force of a some degree, is applied to a contact surface of the engaging hole. Therefore, a damage of the impeller may possibly occur.

Furthermore, there is known another type of fuel pump, in which both of the cross section of the engaging hole and the cross-section of the one end portion of the shaft have an I-shape, so that two contact surfaces of the one end portion of the shaft simultaneously contact two contact surfaces of an inner wall of the engaging hole of the impeller. However, in the case of the impeller, which is molded through the injection molding, it is difficult to form the impeller such that the two contact surfaces of the impeller can simultaneously contact the two contact surfaces of the shaft. Therefore, at the time of contacting the shaft against the impeller, only one of the two contact surfaces of the shaft may possibly contact the impeller to possibly cause the damage of the impeller.

CITATION LIST Patent Literature(s) Patent Literature 1: JPH11-082208A SUMMARY OF THE INVENTION

It is an objective of the present disclosure to provide a fuel pump, which can effectively limit a damage of an impeller.

According to the present disclosure, there is provided a fuel pump, which includes a pump case, a stator, a rotor, a shaft and an impeller. The pump case includes a suction port, through which fuel is drawn into the pump case, and a discharge port, through which the fuel is discharged from the pump case. A plurality of windings is wound around the stator, which is configured into a tubular form, and the stator is received in the pump case. The rotor is rotatably placed on a radially inner side of the stator. The shaft is coaxial with the rotor and rotates integrally with the rotor. The impeller includes an engaging hole, which receives one end portion of the shaft. When the impeller is rotated integrally with the shaft, the impeller pressurizes the fuel drawn through the suction port and discharges the pressurized fuel through the discharge port. The one end portion of the shaft includes at least one shaft side contact surface that is contactable with the impeller. The engaging hole includes at least one impeller side contact surface, which opposes the at least one shaft side contact surface and is contactable with the at least one shaft side contact surface. The impeller includes at least one deformation enabling space that is deformed when the at least one shaft side contact surface and the at least one impeller side contact surface contact with each other.

In the fuel pump of the present disclosure, the shaft and the impeller are formed such that the shaft and the impeller integrally rotate while the shaft side contact surface and the impeller side contact surface contact with each other. When the impeller is rotated integrally with the shaft, the shaft side contact surface and the impeller side contact surface may possibly contact with each other in an incorrect state depending on the processing accuracy of the engaging hole and/or the position of the shaft relative to the engaging hole. In the impeller of the fuel pump of the present disclosure, when the shaft side contact surface and the impeller side contact surface contact with each other, the deformable space is deformed by a force, which is applied from the shaft to the impeller. When the deformable space is deformed, the resiliently deformable amount of the impeller is increased. Therefore, the shape of the engaging hole is changed, and the shaft side contact surface correctly contacts the impeller side contact surface. As discussed above, in the fuel pump of the present disclosure, the shaft side contact surface and the impeller side contact surface can correctly contact with each other through the deformation of the deformation enabling space without being influenced by the processing accuracy of the engaging hole and/or the position of the shaft relative to the engaging hole. Thus, the surface pressure, which is applied to the impeller at the time of rotating the shaft, becomes small, and the damage of the impeller can be effectively limited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a fuel pump according to a first embodiment of the present disclosure.

FIG. 2 is a top view of an impeller of the fuel pump of the first embodiment.

FIGS. 3(a) to 3(d) are schematic diagrams for describing an operation of the fuel pump according to the first embodiment.

FIG. 4 is a top view of an impeller of a fuel pump according to a second embodiment of the present disclosure.

FIG. 5 is a top view of an impeller of a fuel pump according to a third embodiment of the present disclosure.

FIG. 6 is a top view of an impeller of a fuel pump according to a fourth embodiment of the present disclosure.

FIG. 7 is a top view of an impeller of a fuel pump according to a fifth embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Various embodiments of the present disclosure will be described with reference to the accompanying drawings.

First Embodiment

A fuel pump according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 3(d).

The fuel pump 1 includes a motor device 3, a pump device 4, a housing 20, a pump cover 60 and a cover end 40. In the fuel pump 1, the motor device 3 and the pump device 4 are received in a space, which is formed by the housing 20, the pump cover 60 and the cover end 40. The fuel pump 1 draws fuel from a fuel tank (not shown) through a suction port 61, which is indicated in a lower side of FIG. 1, and discharges the fuel toward an internal combustion engine through a discharge port 41, which is indicated in an upper side in FIG. 1. In FIG. 1, the upper side will be referred to as “the upside”, and the lower side will be referred to as “the downside.” The housing 20, the pump cover 60 and the cover end 40 serve as a pump case of the present disclosure.

The housing 20 is configured into a cylindrical tubular form and is made of metal (e.g., iron). The pump cover 60 and the cover end 40 are installed to two end portions 201, 202, respectively, of the housing 20.

The pump cover 60 closes the end portion 201 of the housing 20, at which the suction port 61 is located. A peripheral edge part of the end portion 201 of the housing 20 is inwardly swaged, so that the pump cover 60 is fixed at the inside of the housing 20. Thereby, removal of the pump cover 60 from the housing 20 in the axial direction of the fuel pump 1 is limited. The pump cover 60 includes the suction port 61, which opens toward the downside. An intake passage 62 is formed in an inside of the suction port 61 to extend through the pump cover 60 in a direction (axial direction) of a rotational axis CA52 of a shaft 52. A groove 63, which is connected to the intake passage 62, is formed in a surface of the pump cover 60, which is located on a side where the pump device 4 is placed.

The cover end 40 is made of resin and closes the end portion 202 of the housing 20, at which the discharge port 41 is located. A peripheral edge part of the end portion 202 of the housing 20 is swaged, so that the cover end 40 is fixed in the inside of the housing 20. Therefore, the removal of the cover end 40 from the housing 20 in the axial direction of the fuel pump 1 is limited. The cover end 40 includes the discharge port 41, which opens toward the upside. A discharge passage 42 is formed in an inside of the discharge port 41 to extend through the cover end 40 in the direction of the rotational axis CA52 of the shaft 52. An electric connector portion 43, which receives three connecting terminals 38 to receive an electric power from an outside, is formed in an end portion of the cover end 40, which is located on a side that is opposite from the side where the discharge passage 42 is formed.

A bearing receiving portion 44, which is configured into a generally tubular form, is formed in an inside of the cover end 40, which is placed in the inside of the housing 20. The bearing receiving portion 44 includes a receiving space 440 that is formed in an inside of the bearing receiving portion 44 to receive an end portion 521 of the shaft 52 and a bearing 55. The bearing 55 rotatably supports the end portion 521 of the shaft 52.

The motor device 3 generates a rotational torque through use of a magnetic field that is generated when the electric power is supplied to the motor device 3. The motor device 3 includes a stator 10, a rotor 50 and the shaft 52. The motor device 3 of the fuel pump 1 of the first embodiment is a brushless motor that senses a position of the rotor 50 relative to the stator 10 through sensing of rotation of the shaft 52.

The stator 10 is configured into a cylindrical tubular form and is received at a radially outer side location in the inside of housing 20. The stator 10 includes six cores 12, six bobbins, six windings and the three connecting terminals. The stator 10 is integrally formed through resin molding of these components.

Each core 12 is formed by stacking a plurality of plates, which are made of a magnetic material (e.g., iron). The cores 12 are arranged one after another in a circumferential direction to radially oppose a magnet 54 of the rotor 50.

The bobbins 14 are made of a resin material. At the time of manufacturing, the cores 12 are inserted into and integrated with the bobbins 14, respectively. Each bobbin 14 includes an upper end portion 141, an insert portion 142 and a lower end portion 143. The upper end portion 141 is formed on the discharge port 41 side. Each core 12 is inserted into the insert portion 142 of the corresponding bobbin 14. The lower end portion 143 is formed on the suction port 61 side.

Each of the windings is, for example, a copper wire that has an outer surface coated with a dielectric film. Each winding is wound around the corresponding bobbin 14, into which the core 12 is inserted, to form one coil. Each winding includes an upper end winding portion 161, an insert winding portion (not shown) and a lower end winding portion 163. The upper end winding portion 161 is wound around the upper end portion 141 of the corresponding bobbin 14. The insert winding portion is wound around the insert portion 142 of the bobbin 14. The lower end winding portion 163 is wound around the lower end portion 143 of the bobbin 14. The windings are electrically connected to the connecting terminals 38 received in the electric connector portion 43.

Each connecting terminal 38 extends through the cover end 40 and is fixed to the upper end portion 141 of the corresponding bobbin 14. In the fuel pump 1 of the first embodiment, the number of the connecting terminals 38 is three, and these connecting terminals 38 receive the three-phase electric power from an electric power source device (not shown).

The rotor 50 is rotatably received on the inner side of the stator 10. The rotor 50 includes the magnet 54, which is placed to surround an iron core 53. The magnet 54 is magnetized to have N-poles and S-poles, which are alternately arranged one after another in the circumferential direction. In the first embodiment, the number of pole pairs of the N-pole and the S-pole is two, so that the total number of the poles is four.

The shaft 52 is securely press fitted into a shaft hole 51 of the rotor 50, which extends along a central axis of the rotor 50, and the shaft 52 is rotated integrally with the rotor 50. An end portion 522 of the shaft 52, which serves as one end portion of the shaft 52 of the present disclosure and is located on the suction port 61 side, is connected to the pump device 4.

The end portion 522 of the shaft 52 includes a shaft first planar surface (serving as a shaft side first contact surface or a shaft side contact surface) 523, which extends in the vertical direction and is formed as a planar surface, and a shaft second planar surface (serving as a shaft side second contact surface or a shaft side contact surface) 524, which is formed as a planar surface and is generally parallel to the shaft first planar surface 523. The end portion 522 of the shaft 52 includes a shaft first curved surface 525 and a shaft second curved surface 526. The shaft first curved surface 525 connects between one side of the shaft first planar surface 523 and one side of the shaft second planar surface 524 and is formed as a curved surface. The shaft second curved surface 526 connects between another side of the shaft first planar surface 523 and another side of the shaft second planar surface 524 and is formed as a curved surface. In this way, a cross section of the end portion 522 of the shaft 52, which is taken in a direction perpendicular to the rotational axis CA52 of the shaft 52, has a generally I-shape.

The pump device 4 pressurizes the fuel drawn through the suction port 61 and discharges the pressurized fuel into the inside of the housing 20 through use of the rotational torque generated by the motor device 3. The pump device 4 includes a pump casing 70 and an impeller 65.

The pump casing 70 is configured into a generally circular disk form and is placed between the pump cover 60 and the stator 10. A through-hole 71 is formed in a center portion of the pump casing 70 to extend through the pump casing 70 in a plate thickness direction of the pump casing 70. A bearing 56 is fitted into the through-hole 71. The bearing 56 rotatably supports the end portion 522 of the shaft 52. In this way, the rotor 50 and the shaft 52 are rotatable relative to the cover end 40 and the pump casing 70.

In a surface of the pump casing 70, which is axially placed on the impeller 65 side, a groove 73 is formed at a location that is opposed to the groove 63 of the pump cover 60. A fuel passage 74, which extends through the pump casing 70 in the direction of the rotational axis CA52 of the shaft 52, is communicated with the groove 73.

The impeller 65 is made of resin and is configured into a generally circular disk form. The impeller 65 is received in a pump chamber 72, which is formed between the pump cover 60 and the pump casing 70.

An engaging hole 66 is formed generally in a center of the impeller 65. A cross section of the engaging hole 66 is configured to have a generally I-shape to correspond with the cross section of the end portion 522 of the shaft 52. The end portion 522 of the shaft 52 is received in the engaging hole 66. In this way, the impeller 65 is rotated in the pump chamber 72 by the rotation of the shaft 52. The details of the shape of the impeller 65 will be described later.

The impeller 65 includes a plurality of tilt surfaces 64, which are placed at a location that corresponds to the grooves 63, 73. As shown in FIG. 2, the tilt surfaces 64 are arranged one after another at generally equal intervals in the circumferential direction in a radially outer end part of the impeller 65.

In the fuel pump 1 of the first embodiment, when the electric power is supplied to the windings of the motor device 3 through the terminals 38, the impeller 65 is rotated together with the rotor 50 and the shaft 52. When the impeller 65 is rotated, the fuel in the fuel tank, which receives the fuel pump 1, is guided to the groove 63 through the suction port 61. The fuel, which is guided to the groove 63, is pressurized through the rotation of the impeller 65 and is guided to the groove 73. The pressurized fuel is guided to an intermediate chamber 75, which is formed between the pump casing 70 and the motor device 3, through the fuel passage 74. The fuel, which is guided to the intermediate chamber 75, is conducted through a fuel passage 77, which is formed between the rotor 50 and the stator 10, a fuel passage 78, which is formed between an outer wall of the shaft 52 and inner walls 144 of the bobbins 14, and a fuel passage 79, which is formed on a radially outer side of the bearing receiving portion 44. Furthermore, the fuel, which is guided to the intermediate chamber 75, is conducted through a fuel passage 76 that is formed between an inner wall of the housing 20 and an outer wall of the stator 10. The fuel, which flows through the fuel passages 76, 77, 78, 79, is discharged to the outside of the fuel pump 1 through the discharge passage 42 and the discharge port 41.

The fuel pump 1 of the first embodiment has a characteristic feature with respect to a shape of the impeller 65. Now, the details of the shape of the impeller 65 will be described with reference to FIGS. 2 to 3(d). FIG. 2 is a top view of the impeller 65. FIGS. 3(a) to 3(d) are schematic diagrams showing a positional relationship between the engaging hole 66 and the shaft 52 at the time of driving the fuel pump 1. Here, it should be noted that the shape of the engaging hole 66 of FIGS. 3(b) to 3(d) is exaggerated in comparison to the actual shape of the engaging hole 66 for the descriptive purpose.

The engaging hole 66 of the impeller 65 is formed by an impeller first planar surface (serving as an impeller side first contact surface or an impeller side contact surface) 661, an impeller second planar surface (serving as an impeller side second contact surface or an impeller side contact surface) 662, an impeller first curved surface (serving as an engaging hole first forming surface or an engaging hole forming surface) 663 and an impeller second curved surface (serving as an engaging hole second forming surface or an engaging hole forming surface) 664.

The impeller first planar surface 661 is a planar surface that is formed to extend in a direction (axial direction) of a central axis CA66 of the engaging hole 66. The central axis CA66 also serves as a central axis of the impeller 65. The impeller first planar surface 661 is formed at a corresponding location, at which the impeller first planar surface 661 opposes the shaft first planar surface 523. When the shaft 52 is rotated, the impeller first planar surface 661 is contactable with the shaft first planar surface 523.

The impeller second planar surface 662 is a planar surface that is formed to extend in the direction of the central axis CA66. The impeller second planar surface 662 is generally parallel to the impeller first planar surface 661. The impeller second planar surface 662 is formed at a corresponding location, at which the impeller second planar surface 662 opposes the shaft second planar surface 524. When the shaft 52 is rotated, the impeller second planar surface 662 is contactable with the shaft second planar surface 524.

The impeller first curved surface 663 connects between one side of the impeller first planar surface 661, which is parallel to the central axis CA66, and one side of the impeller second planar surface 662, which is parallel to the central axis CA66. A cross section of the impeller first curved surface 663 is generally configured into a shape of an arc, which is centered at the central axis CA66 and is radially outwardly bulged. A first groove (serving as a deformation enabling space) 665 is formed generally in a center (circumferential center) of the impeller first curved surface 663.

The impeller second curved surface 664 connects between another side of the impeller first planar surface 661, which is parallel to the central axis CA66, and another side of the impeller second planar surface 662, which is parallel to the central axis CA66. A cross section of the impeller second curved surface 664 is generally configured into a shape of an arc, which is centered at the central axis CA66 and is radially outwardly bulged. A second groove (serving as a deformation enabling space) 666 is formed generally in a center (circumferential center) of the impeller second curved surface 664.

The first groove 665 is configured into a form of a slit and extends from the impeller first curved surface 663 in the radially outward direction. The first groove 665 is formed to communicate with the engaging hole 66 and extends through the impeller 65 in the direction of the central axis CA66.

The second groove 666 is configured into a form of a slit and extends from the impeller second curved surface 664 in the radially outward direction. The second groove 666 is formed to communicate with the engaging hole 66 and extends through the impeller 65 in the direction of the central axis CA66.

The first groove 665 and the second groove 666 extend in opposite directions, respectively, which are opposite to each other when the first groove 665 and the second groove 666 are viewed from the central axis CA66. Furthermore, a radial length of the first groove 665 and a radial length of the second groove 666 are equal to each other.

Now, the operation and advantages of the fuel pump 1 of the first embodiment will be described with reference to FIGS. 3(a) to 3(d).

In the fuel pump 1 of the first embodiment, as shown in FIG. 3(a), it is desirable to satisfy the relationship of that when the shaft first planar surface 523 of the shaft 52 and the impeller first planar surface 661 of the engaging hole 66 are placed parallel to each other, the shaft second planar surface 524 of the shaft 52 and the impeller second planar surface 662 of the engaging hole 66 are placed parallel to each other.

However, in the case of the impeller 65, which is made of resin and is formed through injection molding, it is difficult to form the impeller 65 in a manner that satisfies the above relationship. Therefore, in some cases, for example, in a state where the shaft first planar surface 523 and the impeller first planar surface 661 are placed parallel to each other, the shaft second planar surface 524 and the impeller second planar surface 662 may not be parallel to each other.

For instance, in some cases, as shown in FIG. 3(b), the engaging hole 66 may be formed such that although the shaft first planar surface 523 and the impeller first planar surface 661 are held parallel to each other, the shaft second planar surface 524 and the impeller second planar surface 662 are not parallel to each other, and an intersection line 667 between the impeller second planar surface 662 and the impeller second curved surface 664 is held further away from the point along the central axis CA66 of the engaging hole 66.

In the case of the engaging hole 66, which is configured into the shape shown in FIG. 3(b), when the shaft 52 is rotated in a direction R1 indicated by a solid arrow, the shaft first planar surface 523 and the impeller first planar surface 661 contact with each other, and the shaft second planar surface 524 and the impeller second planar surface 662 are spaced away from each other. The shaft 52 and the impeller 65 are further rotated in the direction R1 in this state. At this time, a force F1 is applied between the shaft first planar surface 523 and the impeller first planar surface 661 in a direction that is from the shaft first planar surface 523 to the impeller first planar surface 661. Because of the applied force F1, the impeller 65 is deformed such that the first groove 665 is expanded, as shown in FIG. 3(d). Due to the deformation of the first groove 665, the shape of the engaging hole 66 is changed such that the shaft second planar surface 524 and the impeller second planar surface 662, which were previously spaced from each other, now contact with each other. In FIG. 3(d), a dotted line indicates the shape of the engaging hole 66 and the shape of the first groove 665 before the occurrence of the deformation of the first groove 665.

Here, it is described that the two planar surfaces of the shaft 52 contact the two planar surfaces of the impeller 65 due to the expansion of the first groove 665. This phenomenon may also occur in the second groove 666.

Now, advantages of the first embodiment will be described.

(a) In the fuel pump 1 of the first embodiment, when the shaft 52 contacts one of the impeller first planar surface 661 and the impeller second planar surface 662 upon rotation of the shaft 52 in the engaging hole 66, the first groove 665 or the second groove 666 is deformed to cause the change in the shape of the engaging hole 66. When the shape of the engaging hole 66 is changed, the other one of the shaft first planar surface 523 and the shaft second planar surface 524, which does not contact the one of the impeller first planar surface 661 and the impeller second planar surface 662, contacts the other one of the impeller first planar surface 661 and the impeller second planar surface 662. Thereby, the two planar surfaces of the shaft 52 contact the inner wall of the engaging hole 66. In this way, the rotational torque of the shaft 52 is applied to both of the impeller first planar surface 661 and the impeller second planar surface 662, and thereby the surface pressure of the rotational torque applied to the impeller 65 is reduced. Therefore, the surface pressure, which is applied to the impeller 65, becomes relatively small, and thereby it is possible to effectively limit the damage of the impeller 65 caused by the rotational torque of the shaft 52.

(b) Furthermore, in the fuel pump 1 of the first embodiment, at the time of molding the impeller 65 through the injection molding, it is no longer required to precisely control the parallelism of the impeller first planar surface 661 relative to the shaft first planar surface 523 and the parallelism of the impeller second planar surface 662 relative to the shaft second planar surface 524. Thereby, the two planar surfaces of the shaft 52 can contact the two planar surfaces of the engaging hole 66 while the number of the manufacturing steps of the fuel pump 1 is reduced. Therefore, the manufacturing costs of the fuel pump 1 can be reduced.

(c) The first groove 665 and the second groove 666 are formed in the center of the impeller first curved surface 663 and the center of the impeller second curved surface 664, respectively, which are opposed to each other. The first groove 665 and the second groove 666 extend for the same length in the two opposite directions, respectively, which are opposite to each other when the two opposite directions are viewed from the central axis CA66. In this way, when the rotational torque of the shaft 52 is applied to the impeller first planar surface 661 or the impeller second planar surface 662, the impeller 65 is deformed to the similar shape. Thereby, the concentration of the stress on any particular portion of the impeller 65 can be limited. Thus, it is possible to limit the damage of the impeller 65 caused by the rotational torque of the shaft 52.

Second Embodiment

Next, a fuel pump according to a second embodiment of the present disclosure will be described with reference to FIG. 4. The second embodiment differs from the first embodiment with respect to the shape of the impeller. In the following description, components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described further.

FIG. 4 is a top view of an impeller 67 of a fuel pump according to the second embodiment. An engaging hole 68 is formed generally in a center of the impeller 67. The end portion 522 of the shaft 52 is received in the engaging hole 66.

A cross section of the engaging hole 68 is configured to have a generally I-shape to correspond with the cross section of the end portion 522 of the shaft 52. The engaging hole 68 is formed by an impeller first planar surface (serving as an impeller side first contact surface or an impeller side contact surface) 681, an impeller second planar surface (serving as an impeller side second contact surface or an impeller side contact surface) 682, an impeller first curved surface (serving as an engaging hole first forming surface or an engaging hole forming surface) 683 and an impeller second curved surface (serving as an engaging hole second forming surface or an engaging hole forming surface) 684.

The impeller first planar surface 681 is formed to extend in a direction of a central axis CA67 of the engaging hole 68. The impeller first planar surface 681 is formed at a corresponding location, at which the impeller first planar surface 681 opposes the shaft first planar surface 523. When the shaft 52 is rotated, the impeller first planar surface 681 is contactable with the shaft first planar surface 523.

The impeller second planar surface 682 is a planar surface that is formed to extend in the direction of the central axis CA67. The impeller second planar surface 682 is generally parallel to the impeller first planar surface 681. The impeller second planar surface 682 is formed at a corresponding location, at which the impeller second planar surface 662 opposes the shaft second planar surface 524. When the shaft 52 is rotated, the impeller second planar surface 682 is contactable with the shaft second planar surface 524.

The impeller first curved surface 683 connects between one side of the impeller first planar surface 681, which is parallel to the central axis CA67, and one side of the impeller second planar surface 682, which is parallel to the central axis CA67. A cross section of the impeller first curved surface 683 is configured into a shape of an arc, which is centered at the point along the central axis CA67 and is radially outwardly bulged. A first groove (serving as a deformation enabling space) 685 is formed generally in a center (circumferential center) of the impeller first curved surface 683.

The impeller second curved surface 684 connects between another side of the impeller first planar surface 681, which is parallel to the central axis CA67, and another side of the impeller second planar surface 682, which is parallel to the central axis CA67. A cross section of the impeller second curved surface 684 is configured into a shape of an arc, which is centered at the point along the central axis CA67 and is radially outwardly bulged. A second groove (serving as a deformation enabling space) 686 is formed generally in a center (circumferential center) of the impeller second curved surface 684.

The first groove 685 is configured into a form of a slit and extends from the impeller first curved surface 683 in the radially outward direction. The first groove 685 is formed to communicate with the engaging hole 68 and extends through the impeller 67 in the direction of the central axis CA67. The second groove 686 is configured into a form of a slit and extends from the impeller second curved surface 684 in the radially outward direction. The second groove 686 is formed to communicate with the engaging hole 68 and extends through the impeller 67 in the direction of the central axis CA67.

The first groove 685 and the second groove 686 extend in two opposite directions, respectively, which are opposite to each other when the two directions are viewed from the central axis CA67. Furthermore, a radial length of the first groove 685 and a radial length of the second groove 686 are equal to each other. Here, it is assumed that an imaginary circle, which is centered at the central axis CA67 and circumferentially connects radially inner side parts of the tilt surfaces 64 of the impeller 67, is an imaginary circle VL64, and an imaginary circle, which is centered at the central axis CA67 and extends along the impeller first curved surface 683 and the impeller second curved surface 684, is an imaginary circular VL68. In such a case, a radially outer side wall surface 687 of the first groove 685, and a radially outer side wall surface 688 of the second groove 686, are formed on a radially inner side of an intermediate imaginary circle VL67 that is radially equally spaced (by a distance D2 in FIG. 4) from both of the imaginary circle VL64 and the imaginary circle VL68, as shown in FIG. 4.

In the fuel pump of the second embodiment, the first groove 685 and the second groove 686 are formed on the radially inner side of the intermediate imaginary circle VL67. In this way, the impeller 67 can be appropriately deformed by the action of the shaft 52. Therefore, the fuel pump of the second embodiment achieves the advantages, which are similar to those of the first embodiment. Also, in the fuel pump of the second embodiment, the tolerable amount of deformation is increased in comparison to that of the first embodiment. Thereby, the damage of the impeller 67 caused by the rotational torque of the shaft 52 can be further effectively limited.

Third Embodiment

Next, a fuel pump according to a third embodiment of the present disclosure will be described with reference to FIG. 5. The third embodiment differs from the first embodiment with respect to the shape of the impeller. In the following description, components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described further.

In the fuel pump of the third embodiment, the impeller 85 includes a plurality of tilt surfaces 84, an engaging hole 86 and a plurality of through-holes (serving as deformation enabling spaces) 87.

Similar to the tilt surfaces 64 of the first embodiment, the tilt surfaces 84 are formed at the location that corresponds to the grooves 63, 73.

Similar to the engaging hole 66 of the first embodiment, a cross section of the engaging hole 86 is configured to have a generally I-shape to correspond with the cross section of the end portion 522 of the shaft 52. The engaging hole 86 is formed by an impeller first planar surface (serving as an impeller side first contact surface or an impeller side contact surface) 861, which is contactable with the shaft first planar surface 523, and an impeller second planar surface (serving as an impeller side second contact surface or an impeller side contact surface) 862, which is contactable with the shaft second planar surface 524.

The through-holes 87 extend through the impeller 85 in a direction of a central axis CA85. In the fuel pump of the second embodiment, the total number of the through-holes 87 is six, and these through-holes 87 are arranged one after another at equal intervals along an imaginary circle, which is located on a radially outer side of the engaging hole 86 and is centered at a point along the central axis CA85 of the engaging hole 86. Each of the through-holes 87 is formed at a corresponding location which is point symmetric to another one of the through-holes 87 about a symmetric point that is a point along the central axis CA85.

In the fuel pump of the third embodiment, when the shaft 52 is rotated in the engaging hole 86 of the impeller 85, only one of the shaft first planar surface 523 and the shaft second planar surface 524 of the shaft 52 may contact the inner wall of the engaging hole 86 in some cases. In such a case, the shape of the engaging hole 86 is changed due to the deformation of the through-holes 87, and the other one of the shaft first planar surface 523 and the shaft second planar surface 524 of the shaft 52, which was not previously in contact with the inner wall of the engaging hole 86, now contacts the inner wall of the engaging hole 86. In this way, the fuel pump of the third embodiment can achieve the advantages, which are similar to the advantages discussed in the sections (a) and (b) of the first embodiment, can be achieved. Furthermore, the through-holes 87 are arranged one after another at equal intervals along the imaginary circle, which is centered at the point along the central axis CA85, and each of the through-holes 87 is formed at the corresponding location which is point symmetric to another one of the through-holes 87 about the symmetric point that is the point along the central axis CA85. In this way, when the rotational torque of the shaft 52 is applied to the impeller first planar surface 861 or the impeller second planar surface 862, the impeller 85 is deformed to the similar shape. Thereby, the concentration of the stress (force) on any particular portion of the impeller 85 can be limited. Thus, it is possible to limit the damage of the impeller 85 caused by the rotational torque of the shaft 52.

Fourth Embodiment

Next, a fuel pump according to a fourth embodiment of the present disclosure will be described with reference to FIG. 6. The fourth embodiment differs from the third embodiment with respect to the shape of the impeller. In the following description, components, which are similar to those of the third embodiment, will be indicated by the same reference numerals and will not be described further.

FIG. 6 is a top view of an impeller 88 of a fuel pump according to the fourth embodiment. The impeller 88 includes the tilt surfaces 84, the engaging hole 86 and a plurality of through-holes (serving as deformation enabling spaces) 89.

The through-holes 89 extend through the impeller 88 in the direction of the central axis CA88. In the fuel pump of the fourth embodiment, the total number of the through-holes 89 is six, and these through-holes 89 are arranged one after another at equal intervals along an imaginary circle, which is located on a radially outer side of the engaging hole 86 and is centered at a point along the central axis CA88 of the engaging hole 86.

Here, it is assumed that an imaginary circle, which is centered at the central axis CA88 and circumferentially connects radially inner side parts of the tilt surfaces 84 located at the radially outer side in the impeller 88, is an imaginary circle VL84, and an imaginary circle, which is centered at the central axis CA88 and extends along the impeller first curved surface (serving as the engaging hole forming surface) 863 and the impeller second curved surface (serving as the engaging hole forming surface) 864 of the engaging hole 86, is an imaginary circular VL88. In such a case, the through-holes 89 are formed on a radially inner side of an intermediate imaginary circle VL88 that is radially equally spaced (by a distance D4 in FIG. 6) from both of the imaginary circle VL84 and the imaginary circle VL86, as shown in FIG. 6.

In the fuel pump of the fourth embodiment, the through-holes 89 are formed on the radially inner side of the intermediate imaginary circle VL88. In this way, the impeller 88 can be appropriately deformed by the action of the shaft 52. Therefore, the fuel pump of the fourth embodiment achieves the advantages, which are similar to those of the third embodiment. Also, according to the fourth embodiment, the tolerable amount of deformation is increased in comparison to that of the third embodiment. Thereby, the damage of the impeller 88 caused by the rotational torque of the shaft 52 can be further effectively limited.

Fifth Embodiment

Next, a fuel pump according to a fifth embodiment of the present disclosure will be described with reference to FIG. 7. In the fifth embodiment, the shape of the end portion of the shaft and the shape of the impeller are different from those of the third embodiment. In the following description, components, which are similar to those of the third embodiment, will be indicated by the same reference numerals and will not be described further.

FIG. 7 is a top view of an impeller 95 of a fuel pump according to the fifth embodiment. The impeller 95 includes a plurality of tilt surfaces 94, an engaging hole 96 and a plurality of through-holes (serving as deformation enabling spaces) 991-995.

The tilt surfaces 94 are formed at a location, which corresponds to the groove 63 formed in the pump cover 60 and the groove 73 formed in the pump casing 70.

The cross section of the engaging hole 96 is configured into a generally D-shape to correspond with a cross section of the one end portion 922 of the shaft 92. The engaging hole 96 is formed by an impeller third planar surface (serving as an impeller side third contact surface or an impeller side contact surface) 961 and an impeller curved surface (serving as an engaging hole forming surface) 963. The impeller third planar surface 961 is contactable with a shaft third planar surface (serving as a shaft side third contact surface or a shaft side contact surface) 923 formed in the one end portion 922 of the shaft 92. The impeller curved surface 963 is formed to extend along a shaft third curved surface (serving as a shaft third curved surface or a shaft curved surface) 925. The shaft third curved surface 925 is an arcuately curved surface and connects between two ends of the shaft third planar surface 923, which are generally parallel to a central axis CA95.

The through-holes 991-995 extend through the impeller 95 in the direction of the central axis CA95. In the fuel pump of the fifth embodiment, the impeller 95 includes the five through-holes 991-995. The through-holes 991-995 are arranged one after another at equal intervals along an imaginary circle, which is located on the radially outer side of the engaging hole 96 and is centered at the point along the central axis CA95 of the engaging hole 96. Furthermore, among the through-holes 991-995 of the impeller 95, two of them, i.e., the through-holes 992, 995 are placed adjacent to two points 962, 964, respectively, at each of which the impeller third planar surface 961 and the impeller curved surface 963 are connected with each other.

Here, it is assumed that an imaginary circle, which is centered at the central axis CA95 and circumferentially connects radially inner side parts of the tilt surfaces 94, is an imaginary circle VL94, and an imaginary circle, which is centered at the central axis CA95 and extends along the impeller curved surface 963, is an imaginary circular VL96. In such a case, the through-holes 991-995 are formed on a radially inner side of an intermediate imaginary circle VL98 that is radially equally spaced (by a distance D5 in FIG. 7) from both of the imaginary circle VL94 and the imaginary circle VL96, as shown in FIG. 7.

In the fuel pump of the fifth embodiment, the cross section of the end portion 922 of the shaft 92 has the D-shape, and the cross section of the engaging hole 96 has the D-shape. Here, the total number of the through-holes 991-995 is five, which is the odd number and corresponds to the shape of the engaging hole 96. In this way, unlike the I-shape of the cross section of the engaging hole, which receives the end portion of the shaft and contacts the end portion of the shaft at the two opposed sides of the engaging hole, even in the case of the engaging hole, which has the cross section that has the D-shape to contact with the end portion of the shaft only at the one side of the engaging hole, the impeller 95 can be deformed such that the shaft third planar surface 923 contacts the impeller third planar surface 961. Therefore, in the fifth embodiment, the advantages, which are similar to those of the third embodiment, are achieved.

Furthermore, in the fuel pump of the fifth embodiment, the through-holes 991-995 are formed on the radially inner side of the intermediate imaginary circle VL98. In this way, the impeller 95 can be appropriately deformed by the action of the shaft 52. As a result, the fuel pump of the fifth embodiment can further effectively limit the damage of the impeller 95 caused by the rotational torque of the shaft 92.

Furthermore, in the impeller 95, the number of the through-holes 991-995 is five, which corresponds to the shape of the engaging hole 96. In this way, the weight balance of the impeller 95 is kept uniform throughout the impeller 95, so that occurrence of defects, such as vibrations, at the time of rotation of the impeller 95 can be limited.

Other Embodiments

(A) In the first and second embodiments, the first groove and the second groove are formed as deformation enabling spaces, respectively. In the third to fifth embodiments, the through-holes are formed as deformation enabling spaces, respectively. However, the shape of the deformation enabling space(s) is not limited to any of these shapes. Specifically, the shape of each deformation enabling space can be any other suitable shape as long as the deformation enabling space is formed in the impeller and can be deformed to increase the resiliently deformable amount of the impeller at the time of occurrence of the contact between the shaft and the impeller.

(B) In the above embodiments, the shaft first planar surface (serving as the shaft side first contact surface), the shaft second planar surface (serving as the shaft side second contact surface), the impeller first planar surface (serving as the impeller side first contact surface), and the impeller second planar surface (serving as the impeller side second contact surface) are formed as the planar surfaces, respectively. However, it is not necessarily to form these surfaces as the planar surfaces, respectively. Specifically, any one or more of these surfaces may be formed as, for example, a curved surface or any other suitable form as long as the shaft side first contact surface and the impeller side first contact surface are contactable with each other, and the shaft side second contact surface and the impeller side second contact surface are contactable with each other.

(C) In the above embodiments, the shaft first planar surface (serving as the shaft side first contact surface) and the shaft second planar surface (serving as the shaft side second contact surface) are formed to be generally parallel to each other. Alternatively, the shaft first planar surface and the shaft second planar surface may be formed to be non-parallel to each other.

(D) In the first and second embodiments, the plurality of deformation enabling spaces is formed in the first and second embodiments. Alternatively, it is possible to provide a single deformation enabling space.

(E) In the first and second embodiments, the first groove and the second groove are formed in the center of the impeller first curved surface and the center of the impeller second curved surface, respectively. However, the location of the first groove and the location of the second groove should not be limited to these locations.

(F) In the first and second embodiments, the radial length of the first groove and the radial length of the second groove are equal to each other, and the first groove and the second groove extend to the opposite directions, respectively. However, the relationship between the first groove and the second groove should not be limited to this relationship.

(G) In the third to fifth embodiments, the through-holes are arranged one after another at equal intervals along the imaginary circle, which is centered at the point along the central axis of the impeller, in the impeller, and each of these through-holes is point-symmetric to another one of these through-holes. However, the locations of the through-holes should not be limited to these locations.

(H) In the third and fourth embodiments, the total number of the through-holes of the impeller is six. Furthermore, in the fifth embodiment, the total number of the through-holes of the impeller is five. In the case where the cross section of the engaging hole of the impeller is the I-shape, it is desirable that the total number of the through-holes is even number. Furthermore, in the case where the cross section of the engaging hole of the impeller is the D-shape, it is desirable that the total number of the through-holes is odd number. However, the total number of the through-holes is not limited to any of these.

(I) In the above embodiments, the motor device of the fuel pump is the brushless motor. However, as long as the motor can rotate the shaft in the two directions, i.e., the normal direction and the reverse direction, any other suitable motor, which is other than the brushless motor, may be used.

The present disclosure is not limited to the above embodiments, and the above embodiments may be modified in various ways within the principle of the present disclosure. 

1. A fuel pump comprising: a pump case that includes a suction port, through which fuel is drawn into the pump case, and a discharge port, through which the fuel is discharged from the pump case; a stator, around which a plurality of windings is wound, wherein the stator is configured into a tubular form and is received in the pump case; a rotor that is rotatably placed on a radially inner side of the stator; a shaft that is coaxial with the rotor and rotates integrally with the rotor; and an impeller that includes an engaging hole, which receives one end portion of the shaft, wherein: when the impeller is rotated integrally with the shaft, the impeller pressurizes the fuel drawn through the suction port and discharges the pressurized fuel through the discharge port; the one end portion of the shaft includes a shaft side first contact surface, which is contactable with the impeller, and a shaft side second contact surface, which is parallel to the shaft side first contact surface and is contactable with the impeller; the engaging hole includes an impeller side contact surface, which opposes one of the shaft side first contact surface and the shaft side second contact surface and is contactable with the one of the shaft side first contact surface and the shaft side second contact surface; and the impeller includes at least one deformation enabling space that is deformed when the one of the shaft side first contact surface and the shaft side second contact surface contact the impeller side contact surface.
 2. The fuel pump according to claim 1, wherein: the impeller side contact surface is an impeller side first contact surface, which opposes the shaft side first contact surface and is contactable with the shaft side first contact surface; the engaging hole further includes an impeller side second contact surface, which opposes the shaft side second contact surface and is contactable with the shaft side second contact surface; the at least one deformation enabling space is deformed when the shaft side first contact surface and the impeller side first contact surface contact with each other, or when the shaft side second contact surface and the impeller side second contact surface contact with each other.
 3. The fuel pump according to claim 2, wherein the at least one deformation enabling space is at least one groove that is communicated with the engaging hole.
 4. The fuel pump according to claim 3, wherein: the engaging hole includes: an engaging hole first forming surface that connects between one side of the impeller side first contact surface and one side of the impeller side second contact surface; and an engaging hole second forming surface that connects between another side of the impeller side first contact surface and another side of the impeller side second contact surface; and the at least one groove includes a first groove, which is formed in the engaging hole first forming surface, and a second groove, which is formed in the engaging hole second forming surface.
 5. The fuel pump according to claim 4, wherein the first groove and the second groove extend in opposite directions, respectively, which are opposite to each other, when the first groove and the second groove are viewed from a central axis of the impeller.
 6. The fuel pump according to claim 5, wherein a radial length of the first groove and a radial length of the second groove are equal to each other.
 7. The fuel pump according to claim 5, wherein: the first groove is formed in a center of the engaging hole first forming surface; and the second groove is formed in a center of the engaging hole second forming surface.
 8. The fuel pump according to claim 1, wherein the at least one deformation enabling space is at least one through-hole, which is formed on a radially outer side of the engaging hole and extends through the impeller in an axial direction of a central axis of the impeller.
 9. The fuel pump according to claim 8, wherein: the impeller side contact surface is an impeller side first contact surface, which opposes the shaft side first contact surface and is contactable with the shaft side first contact surface; the engaging hole further includes an impeller side second contact surface, which opposes the shaft side second contact surface and is contactable with the shaft side second contact surface; the at least one through-hole includes a plurality of through-holes, and a total number of the plurality of through-holes is an even number; the plurality of through-holes is deformed when the shaft side first contact surface and the impeller side first contact surface contact with each other, or when the shaft side second contact surface and the impeller side second contact surface contact with each other; and each of the plurality of through-holes is formed at a location which is point symmetric to another one of the plurality of through-holes about a symmetric point that is a point along the central axis of the impeller.
 10. (canceled)
 11. The fuel pump according to claim 8, wherein the plurality of through-holes is arranged one after another at equal intervals along an imaginary circle, which is centered at the central axis of the impeller.
 12. The fuel pump according to claim 1, wherein: the impeller includes: a plurality of tilt surfaces, which are arranged at a radially outer end part of the impeller, wherein the plurality of tilt surfaces pressurize and discharge the fuel through use of rotation of the impeller; and an engaging hole forming surface that is formed to have a cross section configured into a shape of an arc, which is centered at a central axis of the engaging hole, wherein the engaging hole forming surface is connected to an end of the impeller side contact surface; and the at least one deformation enabling space is placed on a radially inner side of an intermediate imaginary circle that is placed at a location that is radially equally spaced from both of: an imaginary circle that is centered at the central axis of the engaging hole and circumferentially connects radially inner side parts of the plurality of tilt surfaces; and an imaginary circle that is centered at the central axis of the engaging hole and circumferentially connects a radially outer side part of the at least one engaging hole forming surface. 